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    <title>Document</title>
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    <script>
        

        let extend = function(){
            return function VueComponent(){
                // console.log("。。。。。。");
            }
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        let student =  extend();
        let book = extend();

        console.log(student === book);


        /*****************************************/
        Vue.extend = function (extendOptions) {
        //  ...
          var Sub = function VueComponent(options) {
              this._init(options);
          };
          
          return Sub;
      };





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